I live in New York, about 30 min from JFK. I have traveled on JetBlue twice going from JFK-FLL, and three times going from JFK-SLC. My experiences on JetBlue were GREAT. From the second you walk in the terminal, you are treated by a very friendly staff, that is actually having fun doing their jobs. All of my flights with them were on time. The planes are awesome. They are new, and very quiet. The free DirectTV is great, too. The only complaint I have with them is that their seat pitch isn't too good. It will probably be fine going from BUF-JFK, but wasn't all that comfortable going from SLC-JFK. I heard they are going to increases seat pitch though.
While your staying in NYC, I would definetly recommend staying in Manhattan. In case you don't know the area real well, while JFK is technically in New York City, is not in a particularly nice area. It is in queens, which will take you a while to get to Manhattan from, using public transportation.
When I go to JFK, I usually try and spot planes in terminal 1. It is a new international terminal. In this terminal there is a food court up the escalators that anyone (non ticketed passangers) can get to. From here you get a great view of Runway 13R/31L.
If you want any more info about the area, feel free to ask.